The present invention relates to an endoscope light source device.
An endoscope has an insertion section, which is inserted into the living body such as the human body, and is used for diagnosis or treatment of organs, collection of specimens, and so forth. The distal end of the insertion section of the endoscope is provided with an imaging element for acquiring an image, and an output window for an illumination light for illuminating an observed region. A light guide formed of a bundle of optical fibers is inserted into the endoscope, and is connected to a white light source such as a xenon lamp to transmit a light from the light source to the distal end of the insertion section.
As an endoscopic illumination method, a method is known in which the light beams emitted from two points at the distal end of an endoscope are used to illuminate a subject, while taking a shadow caused by the illumination light and a light distribution characteristic into consideration. In this case, the light guide is branched into a plurality of guides inside the endoscope to transmit the light beam obtained from one light source as a plurality of light beams inside the endoscope. However, when the light guide is branched inside the endoscope, there arises a problem in that buckling or disconnection is likely to occur in the branch portion of the light guide upon bending of the endoscope. In order to address the problem, JP 07-246186 A has proposed to dispose the branch portion of the light guide closer to the subject than the bending portion of the endoscope.
On the other hand, it has been proposed to employ as a light source a laser light source to cope with the rise in temperature in the surroundings of the light source due to the heat generated by the light source lamp such as a xenon lamp, or the attenuation of light. Further, JP 2006-166983 A has proposed that a plurality of laser light sources are prepared and sequentially changed over upon use for the purpose of performing a high-precision temperature management of the laser light sources. In the endoscope device disclosed in JP 2006-166983 A, a light guide extends from each of the laser light sources, and the light guides are integrated into one guide before the endoscope device, and inserted into the endoscope device. It is stated in JP 2006-166983 A that the endoscope device disclosed in the document sequentially changes over a plurality of laser light sources upon use, thereby enabling the durability of the laser light sources to be enhanced by suppressing the rise in temperature around the laser light sources, and enabling a clear observation image to be obtained even if the endoscope device is used for a long period of time.
FIG. 7 schematically illustrates such an example of the conventional endoscope device as illustrated in JP 2006-166983 A. Referring to FIG. 7, an endoscope system 100 includes an endoscope device 102 and a control device 104, and the control device 104 is provided with a processor 130 and a plurality of laser light sources LD1 and LD2. The endoscope device 102 comprises an insertion section 106, an operation section 108, a universal cord section 110, and a connector section 112. The insertion section 106 includes a soft portion 114 with flexibility, a bending portion 116, and a distal end portion 118. The distal end portion 118 of the insertion section 106 is provided with a phosphor 120, an illumination window 122 for an illumination light, an objective lens (not shown), and a CCD 124.
A light guide 126, which is formed of the light guides connected to the laser light sources LD1 and LD2, respectively, and integrated into one guide before the endoscope device 102, is inserted into the endoscope device 102. The distal end of the light guide 126 reaches the position of the phosphor 120, and inputs the light beams from the laser light sources LD1 and LD2 to the phosphor 120.
The CCD 124 is connected to the processor 130 of the control device 104 by means of a cable (scope cable) 128 for transmitting an imaging signal. The processor 130 converts the imaging signal that has been transmitted from the CCD 124 into a video signal, and then supplies the video signal to a monitor or the like.
However, in the conventional light guide, a large number of, such as one thousand, optical fibers are bundled into the light guide, and hence some of the optical fibers are damaged even in a portion other than the branched portion discussed as a problem in JP 07-246186 A, due to frictions among the optical fibers or difference in tension between the inner curve and the outer curve of a bent fiber in the bending portion or the like, thereby reducing the number of effective optical fibers in use for a long period of time. For that reason, the optical output from the illumination portion is gradually deteriorated. Further, the endoscope using the conventional light guide has problems in that it is very difficult to reduce the diameter of the insertion section, and the minimum bending radius is large.
Further, in the case of a semiconductor laser beam, an optical fiber with a single core is higher in coupling efficiency between a laser beam and an optical fiber than the conventional bundle fiber used for guiding light such as light from a xenon lamp, and can efficiently guide light up to the distal end portion.
Under the above-mentioned circumstances, it is conceivable to independently use the optical fiber with a single core instead of the bundle fiber as a light guide path. The use of the optical fiber with a single core can reduce damage on the optical fibers repetitively used, which is caused by the frictions among the optical fibers, and substantially increase the strength of the optical fibers. Further, it is possible to decrease the diameter of the endoscope insertion section, and reduce the bending radius.
However, even the optical fiber with a single core cannot completely eliminate the risk of its deterioration, buckling, or breaking, which is caused by sliding inside the endoscope when the endoscope is bent. In addition, the optical fiber may be damaged if a big impact or an external factor (such as dust contamination) should occur. In the case of using only one optical fiber with a single core, if the optical fiber is damaged, the optical output becomes zero, and illumination stops.
For example, in the conventional endoscope system 100 illustrated in FIG. 7, when it is assumed that the light guide 126 is replaced with the optical fiber with a single core, even if one of the laser light sources LD1 and LD2 stops light emission, the other laser light source is switchingly used, thereby enabling the illumination light to be ensured. However, when the optical fiber is disconnected, the illumination light from the distal end of the endoscope device 102 completely stops so that the field of view becomes pitch-dark. If illumination stops while the endoscope is inserted into the body, the image of the surroundings cannot be checked when the endoscope is drawn out of the body, resulting in the fear that it is difficult to keep sufficient safety.